OK, this is my last attempt to try to understand this. If I have a
logical formula that evaluates to true or false (a Condition), such as
one I will call ValidCreditCard, and if a Web service somewhere decides
to use this Condition as the value of its preCondition property, then
ValidCreditCard becomes an instance of the Precondition class. If that
Web service disappears, then ValidCreditCard reverts back to the
Condition class.
So, using a formula changes it, and when you stop using it, it changes
back. Or am I still misunderstanding the idea?
Cheers,
Mike
-----Original Message-----
From: Monika Solanki [mailto:monika@dmu.ac.uk]
Sent: Saturday, November 08, 2003 11:10 AM
To: Huhns, Michael
Cc: public-sws-ig@w3.org
Subject: Re: the precondition property in OWL-S 1.0
Hi Michael,
The property that makes it special does not lie in the syntax but in the
semantics. Precondition is a property which is required to be true,
before the execution of the service. So there could be several formulae
that could be classified as Conditions, however if any such formula is
tagged with a qualifier that it is a precondition, it makes a difference
in the interpretation of that Condition for the execution of the
service.
-Monika
Huhns, Michael wrote:
Hi Monika,
If a Precondition is a special kind of Condition, then it must have some
property (or a restriction on some property) that makes it special.
What is this? That is, given a logical formula that evaluates to true
or false, what property does it have that would enable you to determine
whether it is a Condition or Precondition?
Cheers,
Mike Huhns
-----Original Message-----
From: public-sws-ig-request@w3.org [mailto:public-sws-ig-request@w3.org]
On Behalf Of Monika Solanki
Sent: Saturday, November 08, 2003 5:15 AM
To: David Martin
Cc: public-sws-ig@w3.org
Subject: Re: the precondition property in OWL-S 1.0
David Martin wrote:
[Note: this thread is moving to public-sws-ig. After this message,
replies should only be sent to public-sws-ig.]
Marta Sabou wrote:
Monika, Drew,
I completely agree with the proposed solution. This should
definitely be
implemented in the next release.
I also agree, except note that there are 2 proposals "on the table":
I think Monika suggested this:
Process - hasPrecondition - Precondition
where Precondition is a subclass of Condition
whereas Drew seems to be suggesting this:
Process - hasPrecondition - Condition
(with no Precondition class anywhere).
I think we should retain the Precondition class and the hasPrecondition
property. This is because, although Precondition is effectively a
Condition, however it is a "special" kind of Condition. In the process
model, Condition is a general thing, which is also used for
Conditional Effects and Conditional Outputs.
That reminds me - we still have an open issue about the class of an
effect (that is, the range of ceEffect). Currently it's just "Thing",
which isn't very satisfying. Do people feel that it's OK to have
Condition for this range, or do we need something distinct?
- David
Cheers,
Marta
Drew McDermott wrote:
[Monika Solanki, in re DAML-S spec]
Currently in the 1.0 version of the process model, we have the
following
<owl:Class rdf:ID="Precondition" />
- <owl:ObjectProperty rdf:ID="preCondition">
<rdfs:domain rdf:resource="#Precondition" />
<rdfs:range rdf:resource="#Condition" />
</owl:ObjectProperty>
Where, Condition is defined as,
- <owl:Class rdf:ID="Condition">
<rdfs:comment>This is a "place-holder" for now, which awaits
further
work from the DAML/OWL community. An instance of Condition is a
logical
formula that evaluates to true or false. Eventually we expect this
to be
defined elsewhere, as part of a OWL extension allowing for logical
expressions.</rdfs:comment>
</owl:Class>
Somehow I am not able to grasp the utility of the property
"preCondition". Since in this model, we have IOPEs as Classes,
therefore I believe all we need to do is make Precondition a
subclass of
Condition.
<owl:Class rdf:ID="PreCondition">
<rdfs:subClassOf rdf:resource="#Condition" />
</owl:Class>
The property preCondition, introduces redundancy as it is ranging
over
the class "Condition" anyways.
Feedback appreciated in case I missed something.
You're right, as far as I can see. The important property is
hasPrecondition, which connects a Condition to a Process or Process
step. There is no reason for the class Precondition to exist, let
alone a property preCondition linking a Precondition to a Condition
(itself?).
--
-- Drew McDermott
Yale University CS
Dept.
--
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Monika Solanki
Software Technology Research Laboratory(STRL)
De Montfort University
Hawthorn building, H00.18
The Gateway
Leicester LE1 9BH, UK
phone: +44 (0)116 250 6170 intern: 6170
email: monika@dmu.ac.uk
web: http://www.cse.dmu.ac.uk/~monika
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